Working mothers who think of doing part-time jobs with flexible schedules are likely to end up working an increased amount of unpaid overtime, new research has found.

The study, led by researchers from the University of Kent, showed that women who gained schedule control over their work had an increase in the amount of unpaid overtime worked.

This was found to be the case for both professional men (about one hour more a week on average) and women without children (about 40 minutes more a week on average). But, for part-time working mothers the unpaid overtime was around 20 minutes more a week.

The increase may be because part-time working mothers feel the need to work longer to compensate for the possible stigma, perceived or otherwise, attached to them by other workers, especially when their schedules do not match normal working hours, the researchers said.

It may also be that part-time working mothers have a greater ability to work unpaid overtime compared to full-time working mothers.

“More control over your work is supposed to make life easier for workers, particularly those with children. However, it is clear that for many, blurring the boundaries between work and home life expands work to be longer, even when it is unpaid,” said Heejung Chung, from Kent’s School of Social Policy.

“Employers need to be aware of this and ensure staff is not over-stretching themselves and undoing the benefits of flexible working,” Chung added.

For the study, published in the journal Social Indicators Research, the team examined three types of flexible working that people use and how it impacted their workloads.

Flexitime where workers have set weekly hours but can work them within a schedule that suits them;

Teleworking ability to work from home for personal reasons on a regular basis;

Schedule control — where workers are able to determine their own hours and schedules, so long as the job is done.

While for the first two types of flexible working, there was little evidence of an increase in unpaid overtime hours, for those who gained schedule control over their work there was an increase in the amount of unpaid overtime.